I have a small collection of used textbooks for sale on an Internet site. Some of them have been posted for several months; I'm always surprised (and happy) when I get an e-mail that I've sold one and need to ship it to a buyer.
The site conveniently provides a link for a printable packing slip. I usually just grab that page off the printer and stick it in the box before I tape everything up. However, today I wrote a personal note to the buyer of a used book.
I folded a piece of colorful stationary in half like a card and wrote on the inside. I thanked her for buying MY book instead of any of the other duplicate copies of the book that were listed. I added that I hoped she enjoyed using the book. It's a literature compilation and has a lot of great stories in it.
I can't remember the last time I received a personal, hand-written note. It made my day; I hope the person who opens my package feels the same way.